KR20110073038A - Oxide thin film transistor and method of fabricating the same - Google Patents

Abstract

PURPOSE: An oxide thin film transistor and a method for manufacturing the same are provided to secure the superior element characteristic by improving the contact characteristic between an oxide semiconductor and a source/drain electrode. CONSTITUTION: An active layer(124) composed of an oxide semiconductor is formed on a gate insulating film(115a). An n+ oxide layer with the high concentration is formed on the substrate with the active layer. The n+ oxide layer is composed of the oxide semiconductor. A source/drain electrode is formed on the substrate with the n+ oxide layer. A protective layer(115b) is formed on the substrate with the source/drain electrode. A contact hole is formed to expose a part of the drain electrode by eliminating a part of the protective layer. A pixel electrode in electric connection with the drain electrode through the contact hole is formed.

Description

OXIDE THIN FILM TRANSISTOR AND METHOD OF FABRICATING THE SAME

The present invention relates to an oxide thin film transistor and a method of manufacturing the same, and more particularly, AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0) The present invention relates to an oxide thin film transistor using a ternary or quaternary oxide semiconductor composed of a combination thereof as an active layer and a method of manufacturing the same.

Recently, with increasing interest in information display and increasing demand for using a portable information carrier, a lightweight flat panel display (FPD), which replaces a conventional display device, a cathode ray tube (CRT), is used. The research and commercialization of Korea is focused on. In particular, the liquid crystal display (LCD) of the flat panel display device is an image representing the image using the optical anisotropy of the liquid crystal, is excellent in resolution, color display and image quality, and is actively applied to notebooks or desktop monitors have.

The liquid crystal display is largely composed of a color filter substrate and an array substrate, and a liquid crystal layer formed between the color filter substrate and the array substrate.

The active matrix (AM) method, which is a driving method mainly used in the liquid crystal display device, uses an amorphous silicon thin film transistor (a-Si TFT) as a switching device to drive the liquid crystal in the pixel portion. to be.

Hereinafter, a structure of a general liquid crystal display device will be described in detail with reference to FIG. 1.

1 is an exploded perspective view schematically illustrating a general liquid crystal display.

As shown in the figure, the liquid crystal display device is largely a liquid crystal layer (liquid crystal layer) formed between the color filter substrate 5 and the array substrate 10 and the color filter substrate 5 and the array substrate 10 ( 30).

The color filter substrate 5 includes a color filter C composed of a plurality of sub-color filters 7 for implementing colors of red (R), green (G), and blue (B); A black matrix 6 that separates the sub-color filters 7 and blocks light passing through the liquid crystal layer 30, and a transparent common electrode that applies a voltage to the liquid crystal layer 30. 8)

In addition, the array substrate 10 may be arranged vertically and horizontally to define a plurality of gate lines 16 and data lines 17 defining a plurality of pixel regions P. The thin film transistor T, which is a switching element formed in the cross region, and the pixel electrode 18 formed on the pixel region P, are formed.

The color filter substrate 5 and the array substrate 10 are joined to face each other by a sealant (not shown) formed on the outer side of the image display area to form a liquid crystal display panel, and the color filter substrate 5 And the bonding of the array substrate 10 is made through a bonding key (not shown) formed in the color filter substrate 5 or the array substrate 10.

On the other hand, the above-mentioned liquid crystal display device is the most attracting display element until now because of the light weight and low power consumption, but the liquid crystal display device is not a light emitting device but a light receiving device and because of the technical limitations such as brightness, contrast ratio and viewing angle, Development of new display devices that can overcome the disadvantages is actively being developed.

Organic Light Emitting Diode (OLED), one of the new flat panel displays, is self-luminous, so it has better viewing angle and contrast ratio than liquid crystal displays, and it is lightweight because it does not require backlight. It is also advantageous in terms of power consumption. In addition, there is an advantage that the DC low-voltage drive is possible and the response speed is fast, in particular, it has an advantage in terms of manufacturing cost.

Recently, studies on the large area of the organic light emitting display have been actively conducted, and in order to achieve this, there is a demand for developing a transistor having stable operation and durability by securing a constant current characteristic as a driving transistor of the organic light emitting display.

Amorphous silicon thin film transistors used in the above-described liquid crystal display device can be fabricated in a low temperature process, but have very low mobility and do not satisfy the constant current bias condition. Polycrystalline silicon thin film transistors, on the other hand, have high mobility and satisfactory constant current test conditions, and are difficult to obtain uniform characteristics, making it difficult to large area and require high temperature processes.

Therefore, an oxide thin film transistor in which an active layer is formed of an oxide semiconductor is being developed. In this case, an oxide thin film transistor having a general bottom gate structure using an oxide semiconductor has a structure without an n + layer unlike an amorphous silicon thin film transistor. It is becoming.

2 is a cross-sectional view schematically illustrating a structure of a general oxide thin film transistor.

As shown in the drawing, a general oxide thin film transistor includes a gate electrode 21 formed on the substrate 10, a gate insulating film 15a formed on the gate electrode 21, and an active semiconductor formed on the gate insulating film 15a. The layer 24, the source / drain electrodes 22 and 23 electrically connected to a predetermined region of the active layer 24, the passivation layer 15b and the drain electrode formed on the source / drain electrodes 22 and 23. 23 and a pixel electrode 18 electrically connected thereto.

The oxide thin film transistor having a general bottom gate structure used as described above is manufactured with a structure without an n + layer unlike an amorphous silicon thin film transistor.

At this time, an oxide thin film transistor using an oxide semiconductor as an active layer has been researched with excellent mobility characteristics, and researches on applying it as a back plane of a next-generation flat panel display have been ongoing. Research into the characteristics of the source / drain electrodes used in the thin film transistor is still insufficient. In particular, studies on the source / drain electrodes have been insufficient in studies on matters such as materials, contact properties, and parasitic resistance.

Currently, a contact problem between an oxide semiconductor of an active layer and the source / drain electrode is being studied. A contact problem between the oxide semiconductor and the source / drain electrode is linear in output characteristics of an oxide thin film transistor. Non-linear characteristics are reported in the area.

The reason why the contact characteristics between the oxide semiconductor and the source / drain electrodes are similar to the Schottky characteristics is due to indium tin oxide (ITO) or indium zinc oxide (Indium Zinc Oxide). IZO) and gold (Au) have a high electron affinity and are not able to form ohmic contact with most oxide semiconductors. Also, zinc oxide (ZnO) -based semiconductors have a difference in deposition conditions. This is because the carrier concentration is controlled and the work function is changed.

The present invention has been made to solve the above problem, a Samsung system consisting of a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0) Another object is to provide an oxide thin film transistor using a tetracomponent oxide semiconductor as an active layer and a method of manufacturing the same.

Another object of the present invention is to provide an oxide thin film transistor and a method for manufacturing the same, which improve contact characteristics between an oxide semiconductor and a source / drain electrode.

Other objects and features of the present invention will be described in the configuration and claims of the invention described below.

In order to achieve the above object, the oxide thin film transistor of the present invention comprises a gate electrode formed on a substrate; A gate insulating film formed on the substrate on which the gate electrode is formed; An active layer formed of an oxide semiconductor on the gate insulating film; A high concentration n + oxide layer formed of an oxide semiconductor on the substrate on which the active layer is formed; A source / drain electrode formed on the substrate on which the n + oxide layer is formed, and electrically connected to a source / drain region of the active layer through the n + oxide layer; A protective layer formed on the substrate on which the source / drain electrodes are formed; A contact hole exposing a portion of the drain electrode by removing a portion of the protective layer; And a pixel electrode electrically connected to the drain electrode through the contact hole, wherein the active layer includes AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, It is characterized by consisting of a ternary or tetracomponent oxide semiconductor consisting of a combination of y, z ≥ 0).

Method of manufacturing an oxide thin film transistor of the present invention comprises the steps of forming a gate electrode on the substrate; Forming a gate insulating film on the substrate on which the gate electrode is formed; Forming an active layer of an oxide semiconductor on the gate insulating film; Forming a high concentration n + oxide layer made of an oxide semiconductor on the substrate on which the active layer is formed; Forming a source / drain electrode electrically connected to a source / drain region of the active layer through the n + oxide layer on the substrate on which the n + oxide layer is formed; Forming a protective layer on the substrate on which the source / drain electrodes are formed; Removing a portion of the protective layer to form a contact hole exposing a portion of the drain electrode; And forming a pixel electrode electrically connected to the drain electrode through the contact hole, wherein the active layer includes AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0) characterized in that consisting of a quarter- or quad-component oxide semiconductor consisting of a combination.

As described above, the oxide thin film transistor and the method of manufacturing the same according to the present invention have an excellent uniformity by using an amorphous oxide semiconductor as an active layer, thereby providing an effect applicable to a large area display.

In addition, the oxide thin film transistor and the method of manufacturing the same according to the present invention provide an effect of securing excellent device characteristics by improving the contact characteristics between the oxide semiconductor and the source / drain electrodes. Therefore, it can be applied as an ultra high resolution large area active matrix liquid crystal display device and a backplane of an organic light emitting diode which is spotlighted as a next generation display.

Hereinafter, exemplary embodiments of an oxide thin film transistor and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a graph showing the results of measuring the electron concentration of the oxide semiconductor according to the oxygen partial pressure, and shows an example in which an a-IGZO semiconductor is used as the oxide semiconductor.

As shown in the figure, it can be seen that as the oxygen partial pressure of the injected oxygen gas is lowered to about 0.01 to 1% when the oxide semiconductor is deposited using a sputter, the electron concentration in the deposited oxide semiconductor increases.

In this case, the oxygen partial pressure represents a ratio of oxygen gas in the total gas in the sputtering equipment. When the oxygen concentration is substantially 0%, the electron concentration is about 1.4x10 ¹⁹ / cm, and the deposited oxide semiconductor is heavily doped. It can be seen that the n + oxide layer can be formed.

As described above, in the fabrication of an oxide thin film transistor using an oxide semiconductor, a high concentration doped n + oxide layer can be formed by controlling the electron concentration of the oxide semiconductor by lowering and depositing an oxygen partial pressure. In particular, by using this to form a high concentration of n + oxide layer between the oxide semiconductor and the source / drain electrode, it is possible to improve the ohmic contact (ohmic contact) to improve the characteristics of the oxide thin film transistor.

Accordingly, the present invention is characterized by adding a highly doped n + oxide layer between the active layer and the source / drain electrode in the process of manufacturing an oxide thin film transistor using an oxide semiconductor.

At this time, the oxide semiconductor and n + oxide layer used in the present invention is composed of a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0) It is a compound having a ternary or tetracomponent composition.

In addition, the highly doped n + oxide layer used in the present invention can be deposited using a sputtering equipment, it is possible to control the electron concentration by adjusting the oxygen partial pressure during deposition.

4 is a cross-sectional view schematically illustrating a structure of an oxide thin film transistor according to a first embodiment of the present invention, wherein AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, The structure of an oxide thin film transistor using a ternary or quaternary oxide semiconductor composed of a combination of y, z? 0) as an active layer is schematically shown.

As shown in the figure, the oxide thin film transistor according to the first embodiment of the present invention is a gate electrode 121 formed on a predetermined substrate 110, a gate insulating film 115a formed on the gate electrode 121, the gate Source / drain regions of the active layer 124 through the n + oxide layer 125n and the n + oxide layer 125n of the active layer 124 made of an oxide semiconductor and the heavily doped oxide semiconductor on the insulating film 115a. And source / drain electrodes 122 and 123 electrically connected to each other.

In the oxide thin film transistor according to the first embodiment of the present invention, a protective layer 115b formed on the substrate 110 on which the source / drain electrodes 122 and 123 are formed and a contact hole formed in the protective layer 115b are provided. The pixel electrode 118 is electrically connected to the drain electrode 123 through.

In this case, although not shown in the drawing, the gate electrode 121 is connected to a predetermined gate line, and a portion of the source electrode 122 extends in one direction to be connected to the data line, and the gate line and the data line are connected to a substrate ( 110 is arranged vertically and horizontally to define the pixel region.

Here, the oxide thin film transistor according to the first embodiment of the present invention is a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0) The active layer may be formed using a ternary or tetracomponent oxide semiconductor. For example, the oxide thin film transistor according to the first embodiment of the present invention may form an active layer using an amorphous zinc oxide based semiconductor. As a result, it satisfies high mobility and constant current test conditions, while ensuring uniform characteristics, which can be applied to large-area displays.

The zinc oxide is a material capable of realizing all three properties of conductivity, semiconductivity, and resistance according to oxygen content. An oxide thin film transistor using an amorphous zinc oxide semiconductor material as an active layer is a liquid crystal display and an organic light emitting display. It can be applied to a large area display including.

In addition, a tremendous interest and activity has recently been focused on transparent electronic circuits, and oxide thin film transistors using the amorphous zinc oxide-based semiconductor materials as active layers have high mobility and can be manufactured at low temperatures, thereby making it possible to manufacture the transparent electronic circuits. There is an advantage that can be used.

In particular, the oxide thin film transistor according to the first embodiment of the present invention is characterized in that the active layer is formed of an a-IGZO semiconductor containing heavy metals such as indium (In) and gallium (Ga) in the ZnO. do.

The a-IGZO semiconductor is transparent because it can pass visible light, and the oxide thin film transistor made of the a-IGZO semiconductor has a mobility of 1 to 100 cm ² / Vs and has higher mobility than that of an amorphous silicon thin film transistor. Indicates.

In addition, the a-IGZO semiconductor has a wide band gap, which can manufacture high-purity UV light emitting diodes (LEDs), white LEDs, and other components, and can be processed at low temperatures to produce light and flexible products. It has features that can be.

Furthermore, since the oxide thin film transistor made of the a-IGZO semiconductor exhibits uniform characteristics similar to that of the amorphous silicon thin film transistor, the component structure is as simple as that of the amorphous silicon thin film transistor and has an advantage that it can be applied to a large area display.

In the oxide thin film transistor according to the first embodiment of the present invention having the above characteristics, a high concentration of n + oxide layer is formed between the active layer and the source / drain electrodes, thereby improving the ohmic contact, thereby obtaining excellent device characteristics. Provide effect. Accordingly, the present invention can be applied to an ultra-high resolution large area active matrix liquid crystal display device and a backplane of an organic light emitting diode which is spotlighted as a next generation display, which will be described in detail through the following method of manufacturing an oxide thin film transistor.

5A through 5E are cross-sectional views sequentially illustrating a process of manufacturing the oxide thin film transistor illustrated in FIG. 4.

As shown in FIG. 5A, a predetermined gate electrode 121 is formed on a substrate 110 made of a transparent insulating material.

At this time, the oxide semiconductor applied to the oxide thin film transistor of the present invention can be deposited at a low temperature, it is possible to use a substrate 110 that can be applied to low-temperature processes such as plastic substrate, soda lime glass. In addition, because of the amorphous properties, it is possible to use the large-area display substrate 110.

In addition, the gate electrode 121 is formed by depositing a first conductive layer on the entire surface of the substrate 110 and then selectively patterning the same through a photolithography process (first mask process).

The first conductive layer may include aluminum (Al), aluminum alloy (Al alloy), tungsten (W), copper (Cu), nickel (Ni), chromium (Cr), Low resistance opaque conductive materials such as molybdenum (Mo), titanium (Ti), platinum (platinum; Pt), tantalum (Ta), and the like may be used. In addition, the first conductive layer may be a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), and the conductive material may be stacked in two or more kinds. It can also be formed into a multi-layered structure.

Next, as shown in FIG. 5B, an inorganic insulating film or hafnium oxide (Hf) oxide, such as a silicon nitride film (SiNx) or a silicon oxide film (SiO ₂ ), is formed on the entire surface of the substrate 110 on which the gate electrode 121 is formed. A gate insulating film 115a made of a highly dielectric oxide film such as aluminum oxide is formed.

After forming a first oxide semiconductor layer made of a predetermined oxide semiconductor on the entire surface of the substrate 110 on which the gate insulating film 115a is formed, the gate electrode is selectively patterned through a photolithography process (second mask process). An active layer 124 made of the oxide semiconductor is formed on the upper portion 121.

In this case, the first oxide semiconductor layer is a ternary system or tetracomponent system composed of a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0). For example, the oxide thin film transistor according to the first embodiment of the present invention satisfies high mobility and constant current test conditions by forming the active layer 124 using an amorphous zinc oxide based semiconductor. On the other hand, the uniform characteristics are secured, which has the advantage of being applicable to large area displays.

In addition, as described above, the oxide thin film transistor according to the first embodiment of the present invention is characterized in that the active layer 124 is formed of an a-IGZO semiconductor containing heavy metals such as indium and gallium in ZnO. .

Next, as shown in FIG. 5C, a predetermined second oxide semiconductor layer and a second conductive film are formed on the entire surface of the substrate 110 on which the active layer 124 is formed using sputtering equipment.

In this case, the second conductive layer may use a low resistance opaque conductive material such as aluminum, aluminum alloy, tungsten, copper, nickel, chromium, molybdenum, titanium, platinum, tantalum, etc. to form a source electrode and a drain electrode. In addition, the second conductive layer may be formed of a transparent conductive material such as indium tin oxide, indium zinc oxide, or a multilayer structure in which two or more conductive materials are stacked.

For example, the second oxide semiconductor layer is deposited at a high concentration through patterning, which will be described later, by increasing the electron concentration by lowering the partial pressure of oxygen to about 0.01 to 1% in the deposition condition for depositing the oxide semiconductor constituting the active layer 124. Available as a doped n + oxide layer.

Thereafter, by selectively patterning the second oxide semiconductor layer and the second conductive layer through a photolithography process (third mask process), the highly doped n + oxide layer 125n and the n + oxide layer are formed on the active layer 124. A source electrode 122 and a drain electrode 123 electrically connected to the source and drain regions of the active layer 124 are formed through 125n.

Next, as shown in FIG. 5D, after the passivation layer 115b is formed on the entire surface of the substrate 110 on which the source / drain electrodes 122 and 123 are formed, the photolithography process (the fourth mask process) is optionally performed. The contact hole 140 is formed in the substrate 110 to expose a portion of the drain electrode 123.

As shown in FIG. 5E, after the third conductive film is formed on the entire surface of the substrate 110 on which the protective film 115b is formed, the substrate 110 is selectively removed through a photolithography process (a fifth mask process). A pixel electrode 118 formed of the third conductive layer and electrically connected to the drain electrode 123 through the contact hole 140.

In this case, the third conductive layer includes a transparent conductive material having excellent transmittance such as indium tin oxide or indium zinc oxide to form the pixel electrode 118.

In the meantime, the active layer, the n + oxide layer, and the source / drain electrode use a half-tone mask or a diffraction mask (hereinafter, referred to as a half-tone mask) to include a diffraction mask. It can also be formed through, which will be described in detail through a second embodiment of the present invention.

6 is a cross-sectional view schematically illustrating a structure of an oxide thin film transistor according to a second embodiment of the present invention, wherein AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, The structure of an oxide thin film transistor using a ternary or quaternary oxide semiconductor composed of a combination of y, z? 0) as an active layer is schematically shown.

In this case, the oxide thin film transistor according to the second embodiment of the present invention is the same as the first embodiment of the present invention except that the active layer, the n + oxide layer, and the source / drain electrodes are formed in one mask process. It consists of substantially the same structure as the oxide thin film transistor according to.

As shown in the figure, the oxide thin film transistor according to the second embodiment of the present invention is a gate electrode 221 formed on a predetermined substrate 210, a gate insulating film 215a formed on the gate electrode 221, the gate The source / drain regions of the active layer 224 through the n + oxide layer 225n and the n + oxide layer 225n of the active layer 224 made of an oxide semiconductor and the heavily doped oxide semiconductor on the insulating layer 215a. And source / drain electrodes 222 and 223 electrically connected to each other.

The oxide thin film transistor according to the second embodiment of the present invention has a protective layer 215b formed on the substrate 210 on which the source / drain electrodes 222 and 223 are formed and a contact hole formed in the protective layer 215b. The pixel electrode 218 may be electrically connected to the drain electrode 223 through the pixel electrode 218.

In this case, although not shown in the drawing, the gate electrode 221 is connected to a predetermined gate line, and a portion of the source electrode 222 extends in one direction to be connected to a data line, and the gate line and the data line are connected to a substrate ( The pixels are arranged horizontally and horizontally on the 210.

Here, the oxide thin film transistor according to the second embodiment of the present invention is a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0) The active layer may be formed using a ternary or tetracomponent oxide semiconductor. For example, the oxide thin film transistor according to the second embodiment of the present invention may form an active layer using an amorphous zinc oxide based semiconductor. As a result, it satisfies high mobility and constant current test conditions, while ensuring uniform characteristics, which can be applied to large-area displays.

In particular, the oxide thin film transistor according to the second embodiment of the present invention is an a-IGZO semiconductor containing heavy metals such as indium and gallium in the ZnO in the same manner as the oxide thin film transistor according to the first embodiment of the present invention described above. An active layer is formed.

In the oxide thin film transistor according to the second embodiment of the present invention having the above characteristics, a high concentration of n + oxide layer is formed between the active layer and the source / drain electrodes to improve the ohmic contact, thereby obtaining excellent device characteristics. On the other hand, by using a half-tone mask it is possible to form the active layer, the n + oxide layer and the source / drain electrode in a single mask process, which will be described in detail through the manufacturing method of the oxide thin film transistor.

7A to 7D are cross-sectional views sequentially illustrating a process of manufacturing the oxide thin film transistor illustrated in FIG. 6.

As shown in FIG. 7A, a predetermined gate electrode 221 is formed on a substrate 210 made of a transparent insulating material.

At this time, the oxide semiconductor applied to the oxide thin film transistor of the present invention can be deposited at a low temperature, it is possible to use a substrate 210 that can be applied to low-temperature processes such as plastic substrate, soda lime glass. In addition, because of the amorphous properties, it is possible to use a large-area display substrate 210.

In addition, the gate electrode 221 is formed by depositing a first conductive layer on the entire surface of the substrate 210 and then selectively patterning the same through a photolithography process (first mask process).

Next, as shown in FIG. 7B, an inorganic insulating film such as a silicon nitride film or a silicon oxide film or a gate insulating film made of a high dielectric oxide film such as hafnium oxide or aluminum oxide is formed on the entire surface of the substrate 210 on which the gate electrode 221 is formed. 215a).

A first oxide semiconductor layer, a second oxide semiconductor layer, and a second conductive film formed of a predetermined oxide semiconductor are formed on the entire surface of the substrate 210 on which the gate insulating film 215a is formed.

In this case, the first oxide semiconductor layer is a ternary system or tetracomponent system composed of a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0). For example, the oxide thin film transistor according to the second embodiment of the present invention satisfies high mobility and constant current test conditions by forming the active layer 224 using an amorphous zinc oxide based semiconductor. On the other hand, the uniform characteristics are secured, which has the advantage of being applicable to large area displays.

In addition, as described above, the oxide thin film transistor according to the second embodiment of the present invention is characterized in that the active layer 224 is formed of an a-IGZO semiconductor containing heavy metals such as indium and gallium in the ZnO.

For example, the second oxide semiconductor layer may be deposited by lowering the oxygen partial pressure to about 0.01% by 1% under the deposition conditions of the first oxide semiconductor layer, wherein the first oxide semiconductor layer and the second oxide semiconductor layer are the same. It can be deposited continuously in sputter equipment.

Thereafter, by selectively patterning through a photolithography process (second mask process), the active layer 224 made of the oxide semiconductor on the gate electrode 221 and the highly doped n + oxide layer 225n and the n + oxide. Source / drain electrodes 222 and 223 electrically connected to the source / drain regions of the active layer 224 are formed through the layer 225n.

Next, as shown in FIG. 7C, after the passivation layer 215b is formed on the entire surface of the substrate 210 on which the source / drain electrodes 222 and 223 are formed, the photolithography process (third mask process) is optionally performed. The contact hole 240 is formed in the substrate 210 to expose a portion of the drain electrode 223.

As shown in FIG. 7D, after forming the third conductive film on the entire surface of the substrate 210 on which the protective film 215b is formed, the substrate 210 is selectively removed through a photolithography process (fourth mask process). A pixel electrode 218 formed of the third conductive layer and electrically connected to the drain electrode 223 through the contact hole 240.

Meanwhile, an etch stopper made of a predetermined insulating material may be formed on the channel region of the active layer according to the first and second embodiments of the present invention, and the etch stopper may be a post-process plasma. The role of preventing the carrier concentration of the channel region from being changed by the process is described in detail through the following third embodiment of the present invention.

8 is a cross-sectional view schematically illustrating a structure of an oxide thin film transistor according to a third exemplary embodiment of the present invention, wherein AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, The structure of an oxide thin film transistor using a ternary or quaternary oxide semiconductor composed of a combination of y, z? 0) as an active layer is schematically shown.

In this case, the oxide thin film transistor according to the third exemplary embodiment of the present invention is substantially the same as the oxide thin film transistor according to the first exemplary embodiment of the present invention, except that an etch stopper is formed on the active layer. .

As shown in the figure, the oxide thin film transistor according to the third embodiment of the present invention is a gate electrode 321 formed on a predetermined substrate 310, a gate insulating film 315a formed on the gate electrode 321, the gate An active layer 324 made of an oxide semiconductor on the insulating film 315a, an etch stopper 350 formed of a predetermined insulating material on the active layer 324, an n + oxide layer 325n made of an oxide semiconductor doped with high concentration, and Source / drain electrodes 322 and 323 electrically connected to the source / drain regions of the active layer 324 through the n + oxide layer 325n.

In addition, in the oxide thin film transistor according to the third embodiment of the present invention, a contact formed on the passivation layer 315b and the passivation layer 315b formed on the substrate 310 on which the source / drain electrodes 322 and 323 are formed. The pixel electrode 318 is electrically connected to the drain electrode 323 through a hole.

Although not shown in the drawing, the gate electrode 321 is connected to a predetermined gate line, and a portion of the source electrode 322 extends in one direction to be connected to a data line, and the gate line and the data line are connected to a substrate ( 310 is arranged vertically and horizontally to define the pixel region.

Here, the oxide thin film transistor according to the third embodiment of the present invention is a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0) An active layer may be formed using a ternary or tetracomponent oxide semiconductor. For example, the oxide thin film transistor according to the third embodiment of the present invention may form an active layer using an amorphous zinc oxide semiconductor. As a result, it satisfies high mobility and constant current test conditions, while ensuring uniform characteristics, which can be applied to large-area displays.

In particular, the oxide thin film transistor according to the third embodiment of the present invention is the same as the oxide thin film transistors according to the first and second embodiments of the present invention described above in which ZnO contains heavy metals such as indium and gallium. An active layer is formed of a-IGZO semiconductor.

In the oxide thin film transistor according to the third embodiment of the present invention having the above characteristics, a high concentration of n + oxide layer is formed between the active layer and the source / drain electrode to improve the ohmic contact, thereby ensuring excellent device characteristics. On the other hand, by forming an etch stopper made of a predetermined insulating material on the channel region of the active layer, it is possible to prevent the carrier concentration of the channel region from being changed by the plasma process in a later process, which is the following oxide thin film transistor It will be described in detail through the manufacturing method.

9A through 9F are cross-sectional views sequentially illustrating a process of manufacturing the oxide thin film transistor illustrated in FIG. 8.

As shown in FIG. 9A, a predetermined gate electrode 321 is formed on a substrate 310 made of a transparent insulating material.

At this time, the oxide semiconductor applied to the oxide thin film transistor of the present invention can be deposited at a low temperature, it is possible to use a substrate 310 that can be applied to low-temperature processes such as plastic substrate, soda lime glass. In addition, because of the amorphous properties, it is possible to use a large-area display substrate 310.

In addition, the gate electrode 321 is formed by depositing a first conductive layer on the entire surface of the substrate 310 and then selectively patterning the same through a photolithography process (first mask process).

Next, as shown in FIG. 9B, an inorganic insulating film such as a silicon nitride film and a silicon oxide film or a gate insulating film made of a highly dielectric oxide film such as hafnium oxide or aluminum oxide is formed on the entire surface of the substrate 310 on which the gate electrode 321 is formed. 315a).

In addition, a first oxide semiconductor layer formed of a predetermined oxide semiconductor is formed on the entire surface of the substrate 310 on which the gate insulating film 315a is formed, and then patterned selectively through a photolithography process (second mask process). An active layer 324 made of the oxide semiconductor is formed on the upper portion 321.

In this case, the first oxide semiconductor layer is a ternary system or tetracomponent system composed of a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0). For example, the oxide thin film transistor according to the third embodiment of the present invention satisfies high mobility and constant current test conditions by forming an active layer 324 using an amorphous zinc oxide based semiconductor. On the other hand, the uniform characteristics are secured, which has the advantage of being applicable to large area displays.

In addition, as described above, the oxide thin film transistor according to the third embodiment of the present invention is characterized in that the active layer 324 is formed of an a-IGZO semiconductor containing heavy metals such as indium and gallium in the ZnO.

Next, as shown in FIG. 9C, an insulating layer made of a predetermined insulating material is formed on the entire surface of the substrate 310 on which the active layer 324 is formed, and then selectively selected through a photolithography process (third mask process). The etch stopper 350 made of the insulating material is formed on the active layer 324, specifically, on the channel region of the active layer 324.

Subsequently, as shown in FIG. 9D, a predetermined second oxide semiconductor layer and a second conductive film are formed on the entire surface of the substrate 310 on which the active layer 324 and the etch stopper 350 are formed using sputtering equipment. .

In this case, for example, the second oxide semiconductor layer may be deposited by lowering the oxygen partial pressure to about 0.01 to 1% under deposition conditions for depositing the oxide semiconductor constituting the active layer 324, thereby increasing the electron concentration to increase concentration through patterning, which will be described later. It can be used as the n + oxide layer doped with.

Subsequently, the second oxide semiconductor layer and the second conductive layer are selectively patterned through a photolithography process (fourth mask process) to form a highly doped n + oxide layer 325n and the n + oxide layer on the active layer 324. A source electrode 322 and a drain electrode 323 electrically connected to the source region and the drain region of the active layer 324 are formed through 325n.

Next, as shown in FIG. 9E, a protective film 315b is formed on the entire surface of the substrate 310 on which the source / drain electrodes 322 and 323 are formed, and then selectively selected through a photolithography process (a fifth mask process). The contact hole 340 is formed in the substrate 310 to expose a portion of the drain electrode 323.

As shown in FIG. 9F, after forming a third conductive film on the entire surface of the substrate 310 on which the protective film 315b is formed, the substrate 310 is selectively removed by a photolithography process (sixth mask process). A pixel electrode 318 formed of the third conductive layer and electrically connected to the drain electrode 323 through the contact hole 340.

Meanwhile, the active layer and the etch stopper may be formed through a single mask process by using a half-tone mask, which will be described in detail with reference to the following drawings.

10A through 10E are cross-sectional views sequentially illustrating another manufacturing process of the oxide thin film transistor illustrated in FIG. 8.

As shown in FIG. 10A, a predetermined gate electrode 321 is formed on a substrate 310 made of a transparent insulating material.

In this case, the gate electrode 321 is formed by depositing a first conductive layer on the entire surface of the substrate 310 and then selectively patterning the same through a photolithography process (first mask process).

Next, as shown in FIG. 10B, an oxide semiconductor layer made of a gate insulating film 315a and an oxide semiconductor and an insulating layer made of a predetermined insulating material are formed on the entire surface of the substrate 310 on which the gate electrode 321 is formed. Thereafter, by selectively patterning the photolithography process (second mask process), an active layer 324 made of the oxide semiconductor and an etch stopper 350 made of the insulating material are formed on the gate electrode 321. do.

In this case, the second mask process uses a half-tone mask, which will be described in detail with reference to the following drawings.

11A through 11F are cross-sectional views illustrating the second mask process illustrated in FIG. 10B in detail.

As shown in FIG. 11A, a first oxide semiconductor layer 320 made of a gate insulating film 315a and an oxide semiconductor and an insulating layer made of a predetermined insulating material are formed on the entire surface of the substrate 310 on which the gate electrode 321 is formed. 330 is formed.

In this case, the first oxide semiconductor layer is, for example, a ternary system consisting of a combination of AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y, z ≥ 0). Alternatively, it may be formed of a four-component oxide semiconductor. As described above, as the active layer 324 is formed using an amorphous zinc oxide-based semiconductor, high mobility and constant current test conditions may be satisfied, and uniform characteristics may be secured. It has the advantage of being applicable to the display.

Next, as shown in FIG. 11B, after forming a photoresist film 370 made of a photosensitive material such as a photoresist on the entire surface of the array substrate 310, the photoresist film 370 is formed through a half-tone mask 380. Selectively irradiates light.

In this case, the half-tone mask 380 includes a first transmission region I through which all of the irradiated light is transmitted, a second transmission region II through which only a part of the light is transmitted and a part of the light, and a block to block all of the irradiated light. An area III is provided, and only light transmitted through the half-tone mask 380 is irradiated to the photosensitive film 370.

Subsequently, after the photoresist 370 exposed through the half-tone mask 380 is developed, light passes through the blocking region III and the second transmission region II, as shown in FIG. 11C. The first photoresist pattern 370a to the third photoresist pattern 370c having a predetermined thickness remain in the blocked or partially blocked region, and the photoresist is completely removed in the first transmission region I through which all light is transmitted. The surface of the insulating layer 330 is exposed.

In this case, the first photoresist pattern 370a formed in the blocking region III is thicker than the second photoresist pattern 370b and the third photoresist pattern 370c formed through the second transmission region II. In addition, the photosensitive film is completely removed in a region where all the light is transmitted through the first transmission region I. This is because the photoresist of the positive type is used, and the present invention is not limited thereto. May be used.

Next, as shown in FIG. 11D, using the first photoresist pattern 370a to the third photoresist pattern 370c formed as described above as a mask, the first oxide semiconductor layer and the insulating layer formed thereunder may be selectively selected. When patterning, an active layer 324 made of the oxide semiconductor is formed on the gate electrode 321 of the array substrate 310.

In this case, an insulating layer pattern 330 ′ formed of the insulating material and patterned in substantially the same shape as the active layer 324 is formed on the active layer 324.

Subsequently, when an ashing process of removing a part of the thickness of the first photoresist pattern 370a to the third photoresist pattern 370c is performed, as shown in FIG. 11E, the second transmission region II is formed. The second photoresist pattern and the third photoresist pattern of are completely removed.

In this case, the first photoresist pattern is a fourth photoresist pattern 370a ′ removed by the thickness of the second photoresist pattern and the third photoresist pattern and remains only in the channel region corresponding to the blocking region III.

Subsequently, as shown in FIG. 11F, when the remaining insulating photoresist pattern is selectively patterned using the remaining fourth photoresist pattern 370a ′ as a mask, the active layer 324 of the array substrate 310 is formed. An etch stopper 350 made of the insulating material is formed on the upper portion.

Next, as shown in FIG. 10C, a predetermined second oxide semiconductor layer and a second conductive film are formed on the entire surface of the substrate 310 on which the etch stopper 350 is formed using sputtering equipment.

For example, the second oxide semiconductor layer is deposited at a high concentration through patterning, which will be described later by increasing the electron concentration by lowering the partial pressure of oxygen to about 0.01 to 1% in deposition conditions for depositing the oxide semiconductor constituting the active layer 324. Available as a doped n + oxide layer.

Thereafter, the second oxide semiconductor layer and the second conductive layer are selectively patterned through a photolithography process (third mask process) to thereby form a highly doped n + oxide layer 325n and the n + oxide layer on the active layer 324. A source electrode 322 and a drain electrode 323 electrically connected to the source region and the drain region of the active layer 324 are formed through 325n.

Next, as shown in FIG. 10D, a protective film 315b is formed on the entire surface of the substrate 310 on which the source / drain electrodes 322 and 323 are formed, and then selectively selected through a photolithography process (fourth mask process). The contact hole 340 is formed in the substrate 310 to expose a portion of the drain electrode 323.

As shown in FIG. 10E, after forming the third conductive film on the entire surface of the substrate 310 on which the protective film 315b is formed, the substrate 310 is selectively removed through a photolithography process (a fifth mask process). A pixel electrode 318 formed of the third conductive layer and electrically connected to the drain electrode 323 through the contact hole 340.

As described above, the present invention can be used not only in a liquid crystal display device but also in another display device manufactured using a thin film transistor, for example, an organic light emitting display device in which an organic light emitting element is connected to a driving transistor.

In addition, the present invention has an advantage that it can be used in a transparent electronic circuit or a flexible display by applying an amorphous zinc oxide-based semiconductor material capable of processing at low temperatures while having a high mobility as an active layer.

Many details are set forth in the foregoing description but should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. Therefore, the invention should not be defined by the described embodiments, but should be defined by the claims and their equivalents.

1 is an exploded perspective view schematically showing a general liquid crystal display device.

2 is a cross-sectional view schematically showing the structure of a typical oxide thin film transistor.

3 is a graph showing the results of measuring the electron concentration of the oxide semiconductor according to the oxygen partial pressure.

4 is a cross-sectional view schematically showing the structure of an oxide thin film transistor according to a first embodiment of the present invention.

5A through 5E are cross-sectional views sequentially illustrating a process of manufacturing the oxide thin film transistor illustrated in FIG. 4.

6 is a cross-sectional view schematically showing the structure of an oxide thin film transistor according to a second embodiment of the present invention.

7A to 7D are cross-sectional views sequentially illustrating a manufacturing process of the oxide thin film transistor illustrated in FIG. 6.

8 is a cross-sectional view schematically showing the structure of an oxide thin film transistor according to a third embodiment of the present invention.

9A to 9F are cross-sectional views sequentially illustrating a manufacturing process of the oxide thin film transistor illustrated in FIG. 8.

10A to 10E are cross-sectional views sequentially illustrating another manufacturing process of the oxide thin film transistor illustrated in FIG. 8.

11A to 11F are cross-sectional views illustrating the second mask process shown in FIG. 10B in detail.

DESCRIPTION OF REFERENCE NUMERALS

110 to 310: substrate 115a to 315a: gate insulating film

115b to 315b: protective film 118 to 318: pixel electrode

121 to 321: gate electrode 122 to 322: source electrode

123 to 323: drain electrode 124 to 324: active layer

125n to 325n: n + oxide layer 350: etch stopper

Claims (11)

Forming a gate electrode on the substrate; Forming a gate insulating film on the substrate on which the gate electrode is formed; Forming an active layer of an oxide semiconductor on the gate insulating film; Forming a high concentration n + oxide layer made of an oxide semiconductor on the substrate on which the active layer is formed; Forming a source / drain electrode electrically connected to a source / drain region of the active layer through the n + oxide layer on the substrate on which the n + oxide layer is formed; Forming a protective layer on the substrate on which the source / drain electrodes are formed; Removing a portion of the protective layer to form a contact hole exposing a portion of the drain electrode; And And forming a pixel electrode electrically connected to the drain electrode through the contact hole, wherein the active layer includes AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta). a method of manufacturing an oxide thin film transistor comprising a ternary or quaternary oxide semiconductor composed of a combination of x, y, z ≥ 0). The method of claim 1, wherein the active layer is formed of an amorphous zinc oxide semiconductor. The method of claim 1, wherein the n + oxide layer is formed through a sputter. The oxide thin film according to claim 1, wherein the n + oxide layer is formed to increase the electron concentration by lowering the partial pressure of oxygen to about 0.01 to 1% under deposition conditions for depositing the oxide semiconductor constituting the active layer. Method for manufacturing a transistor. The method of claim 1, wherein the n + oxide layer and the source / drain electrodes are formed in one mask process using a half-tone mask or a diffraction mask. The method of claim 1, further comprising forming an etch stopper made of a predetermined insulating material on the substrate on which the active layer is formed. The method of claim 6, wherein the active layer and the etch stopper are formed in one mask process using a half-tone mask or a diffraction mask. A gate electrode formed on the substrate; A gate insulating film formed on the substrate on which the gate electrode is formed; An active layer formed of an oxide semiconductor on the gate insulating film; A high concentration n + oxide layer formed of an oxide semiconductor on the substrate on which the active layer is formed; A source / drain electrode formed on the substrate on which the n + oxide layer is formed, and electrically connected to a source / drain region of the active layer through the n + oxide layer; A protective layer formed on the substrate on which the source / drain electrodes are formed; A contact hole exposing a portion of the drain electrode by removing a portion of the protective layer; And And a pixel electrode electrically connected to the drain electrode through the contact hole, wherein the active layer includes AxByCzO (A, B, C = Zn, Cd, Ga, In, Sn, Hf, Zr, Ta; x, y , oxide thin film transistor comprising a quarter- or quad-component oxide semiconductor composed of a combination of z ≥ 0). The oxide thin film transistor of claim 8, wherein the active layer is formed of an amorphous zinc oxide semiconductor. The oxide thin film transistor according to claim 8, wherein the n + oxide layer is formed of an oxide semiconductor constituting the active layer. The oxide thin film transistor of claim 8, further comprising an etch stopper formed of a predetermined insulating material on the substrate on which the active layer is formed.

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